Subhas Adam V.

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Subhas

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Adam V.

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0000-0002-7688-6624

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Movement of deep-sea coral populations on climatic timescales

(John Wiley & Sons, 2013-05-30) Thiagarajan, Nivedita ; Gerlach, Dana ; Roberts, Mark L. ; Burke, Andrea ; McNichol, Ann P. ; Jenkins, William J. ; Subhas, Adam V. ; Thresher, Ronald E. ; Adkins, Jess F.

During the past 40,000 years, global climate has moved into and out of a full glacial period, with the deglaciation marked by several millennial-scale rapid climate change events. Here we investigate the ecological response of deep-sea coral communities to both glaciation and these rapid climate change events. We find that the deep-sea coral populations of Desmophyllum dianthus in both the North Atlantic and the Tasmanian seamounts expand at times of rapid climate change. However, during the more stable Last Glacial Maximum, the coral population globally retreats to a more restricted depth range. Holocene populations show regional patterns that provide some insight into what causes these dramatic changes in population structure. The most important factors are likely responses to climatically driven changes in productivity, [O2] and [CO32–].
Suspended PIC, PC, PN data collected along a North Pacific transect between Hawaii and Alaska on R/V Kilo Moana cruise KM1712 in August 2017

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-09-23) Dong, Sijia ; Berelson, William M. ; Adkins, Jess F. ; Subhas, Adam V. ; Rollins, Nick E.

This dataset includes general measurements for in situ pump casts at 5 stations on a transect between Hawaii and Alaska. Data was collected in August 2017 onboard R/V Kilo Moana cruise KM1712. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/860409
Bottle data from R/V Endeavor cruise EN665 in the Gulf of Maine, conducted April 7-12, 2021

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-12-02) Subhas, Adam V.

This dataset is the bottle data for Cruise EN665 on the R/V Endeavor in the Gulf of Maine, conducted April 7-12, 2021. Included are the CTD rosette data along with nutrient and carbonate chemistry analyses (DIC, TA, and d13C-DIC). Data were collected and analyzed by PI Subhas. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/884424
Sinking particle from R/V Kilo Moana cruise KM1910 in June 2019

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-08-24) Church, Matthew J. ; Maloney, Ashley ; Subhas, Adam V. ; Black, Erin ; Kenyon, Jennifer ; White, Angelicque E. ; Goetze, Erica ; Ferron, Sara

Phosphorus, carbon (total and organic), and nitrogen flux and bulk isotope composition (C and N) from 3-day pit trap deployments in June 2019 at station ALOHA during cruise KM1910. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/852779
Compiled global dataset of PIC/POC and bSi concentrations measured by in situ pumps on multiple research cruises conducted from between 1973 and 2013

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-11-28) Pavia, Frank J. ; Dong, Sijia ; Lam, Phoebe J. ; Subhas, Adam V.

This dataset is a compiled global dataset of inorganic and organic carbon and biogenic silica concentrations measured by in situ pumps. We merged the Multiple Unit Large Volume in-situ Filtration System (MULVFS, Bishop et al. 1985) LVP PIC, POC, and bSi dataset published partially in Lam et al. 2011 with new data collected using McLane in-situ pumps equipped with two size-fractionating filters during the GEOTRACES program. The filter sizes generally consist of a 51 micrometer (μm) or 53μm pre-filter that collects large particles, followed by a 0.8μm or 1μm filter that collects smaller particles. We annotate large size fraction particles (>53μm or >51μm) as "LSF", and small size fraction particles (1-53μm or 0.8-51μm) denoted "SSF" (small size fraction). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/883965
In situ experimentally determined dissolution rates of biogenic calcites along a North Pacific transect between Hawaii and Alaska (KM1712 expedition) in August 2017

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-08-03) Berelson, William M. ; Adkins, Jess F. ; Subhas, Adam V. ; Dong, Sijia ; Naviaux, John D.

This dataset includes biogenic and inorganic calcite and aragonite dissolution rates from the CDisK-IV cruise in the North Pacific Ocean, August 2017. We include niskin incubator alkalinity, pH, silicate, phosphate, and nitrate data, as well as calculated saturation state and dissolution rates. Rates are reported in units of g/g/day and also g/cm2/day, normalized by the specific surface areas of the materials used. Dissolution rates of inorganic aragonite and calcite, along with biogenic E. huxleyi liths, a planktic foraminifera assemblage, and a benthic foraminifera Amphistegina species, are provided, for 4 out of the 6 stations occupied on the cruise. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/856409
Carbonate chemistry and CTD data collected along a North Pacific transect between Hawaii and Alaska on R/V Kilo Moana cruise KM1712 in August 2017

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-02-01) Dong, Sijia ; Liu, Xuewu ; Naviaux, John D. ; Subhas, Adam V. ; Rollins, Nick E. ; Adkins, Jess F. ; Berelson, William M.

This dataset includes carbonate chemistry and general measurements from CTD casts at 6 stations between Hawaii and Alaska. Data were collected in August 2017 onboard R/V Kilo Moana. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/836954
Carbonate chemistry and CTD data collected along a North Pacific transect between Hawaii and Alaska on R/V Kilo Moana cruise KM1712 in August 2017

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-01-20) Dong, Sijia ; Liu, Xuewu ; Naviaux, John D. ; Subhas, Adam V. ; Rollins, Nick E. ; Adkins, Jess F. ; Berelson, William M.

This dataset includes carbonate chemistry and general measurements from CTD casts at 6 stations between Hawaii and Alaska. Data were collected in August 2017 onboard R/V Kilo Moana. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/836954
Sinking PIC, PC in shallow sediment traps collected along a North Pacific transect between Hawaii and Alaska on R/V Kilo Moana cruise KM1712 in August 2017

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-09-23) Dong, Sijia ; Berelson, William M. ; Adkins, Jess F. ; Subhas, Adam V. ; Rollins, Nick E.

This dataset includes general measurements for sediment trap casts at 5 stations along a transect between Hawaii and Alaska. Data was collected in August 2017 onboard R/V Kilo Moana cruise KM1712. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/860424
Microbial ecosystem responses to alkalinity enhancement in the North Atlantic Subtropical Gyre

(Frontiers Media, 2022-07-25) Subhas, Adam V. ; Marx, Lukas ; Reynolds, Sarah ; Flohr, Anita ; Mawji, Edward ; Brown, Peter J. ; Cael, B. Barry

In addition to reducing carbon dioxide (CO2) emissions, actively removing CO2 from the atmosphere is widely considered necessary to keep global warming well below 2°C. Ocean Alkalinity Enhancement (OAE) describes a suite of such CO2 removal processes that all involve enhancing the buffering capacity of seawater. In theory, OAE both stores carbon and offsets ocean acidification. In practice, the response of the marine biogeochemical system to OAE must be demonstrably negligible, or at least manageable, before it can be deployed at scale. We tested the OAE response of two natural seawater mixed layer microbial communities in the North Atlantic Subtropical Gyre, one at the Western gyre boundary, and one in the middle of the gyre. We conducted 4-day microcosm incubation experiments at sea, spiked with three increasing amounts of alkaline sodium salts and a 13C-bicarbonate tracer at constant pCO2. We then measured a suite of dissolved and particulate parameters to constrain the chemical and biological response to these additions. Microbial communities demonstrated occasionally measurable, but mostly negligible, responses to alkalinity enhancement. Neither site showed a significant increase in biologically produced CaCO3, even at extreme alkalinity loadings of +2,000 μmol kg−1. At the gyre boundary, alkalinity enhancement did not significantly impact net primary production rates. In contrast, net primary production in the central gyre decreased by ~30% in response to alkalinity enhancement. The central gyre incubations demonstrated a shift toward smaller particle size classes, suggesting that OAE may impact community composition and/or aggregation/disaggregation processes. In terms of chemical effects, we identify equilibration of seawater pCO2, inorganic CaCO3 precipitation, and immediate effects during mixing of alkaline solutions with seawater, as important considerations for developing experimental OAE methodologies, and for practical OAE deployment. These initial results underscore the importance of performing more studies of OAE in diverse marine environments, and the need to investigate the coupling between OAE, inorganic processes, and microbial community composition.
Shallow calcium carbonate cycling in the North Pacific Ocean

(American Geophysical Union, 2022-05-06) Subhas, Adam V. ; Dong, Sijia ; Naviaux, John D. ; Rollins, Nick E. ; Ziveri, Patrizia ; Gray, William R. ; Rae, James W. B. ; Liu, Xuewu ; Byrne, Robert H. ; Chen, Sang ; Moore, Christopher ; Martell-Bonet, Loraine ; Steiner, Zvi ; Antler, Gilad ; Hu, Huanting ; Lunstrum, Abby ; Hou, Yi ; Kemnitz, Nathaniel ; Stutsman, Johnny ; Pallacks, Sven ; Dugenne, Mathilde ; Quay, Paul D. ; Berelson, William M. ; Adkins, Jess F.

The cycling of biologically produced calcium carbonate (CaCO3) in the ocean is a fundamental component of the global carbon cycle. Here, we present experimental determinations of in situ coccolith and foraminiferal calcite dissolution rates. We combine these rates with solid phase fluxes, dissolved tracers, and historical data to constrain the alkalinity cycle in the shallow North Pacific Ocean. The in situ dissolution rates of coccolithophores demonstrate a nonlinear dependence on saturation state. Dissolution rates of all three major calcifying groups (coccoliths, foraminifera, and aragonitic pteropods) are too slow to explain the patterns of both CaCO3 sinking flux and alkalinity regeneration in the North Pacific. Using a combination of dissolved and solid-phase tracers, we document a significant dissolution signal in seawater supersaturated for calcite. Driving CaCO3 dissolution with a combination of ambient saturation state and oxygen consumption simultaneously explains solid-phase CaCO3 flux profiles and patterns of alkalinity regeneration across the entire N. Pacific basin. We do not need to invoke the presence of carbonate phases with higher solubilities. Instead, biomineralization and metabolic processes intimately associate the acid (CO2) and the base (CaCO3) in the same particles, driving the coupled shallow remineralization of organic carbon and CaCO3. The linkage of these processes likely occurs through a combination of dissolution due to zooplankton grazing and microbial aerobic respiration within degrading particle aggregates. The coupling of these cycles acts as a major filter on the export of both organic and inorganic carbon to the deep ocean.
Selective preservation of coccolith calcite in Ontong-Java Plateau sediments

(American Geophysical Union, 2019-11-15) Subhas, Adam V. ; McCorkle, Daniel C. ; Quizon, Alex ; McNichol, Ann P. ; Long, Matthew H.

Dissolution of calcite in deep ocean sediments, which is required to balance global marine CaCO3 production and burial fluxes, is still a poorly understood process. In order to assess the mechanisms of dissolution in sediments, we analyzed four multicore tops taken along a depth transect on the Ontong‐Java Plateau. These cores were taken directly on the equator, and span water column calcite saturation states from ∼0.93 to ∼0.74, allowing us to assess the effect of dissolution on carbonate sediment composition. The top 2 cm of each multicore was sectioned and sieved to separate coccolith from foraminiferal calcite, and the %CaCO3, δ13C, Δ14C, and Mg/Ca were evaluated. The mass ratio of coccoliths to foraminifera increases by a factor of 3 as a function of water depth, reflecting the preferential dissolution of foraminifera. Carbon isotope (δ13C and Δ14C) data suggest that most dissolution takes place at the sediment‐water interface and primarily affects foraminifera. Mg/Ca analyses indicate that the Mg content of the entire foraminiferal assemblage decreases as a function of dissolution. In contrast, coccolith dissolution takes place within the sediments, rather than at the interface. Together these two processes cause coccoliths to be up to 1,000 radiocarbon years younger than foraminifera from the same depth horizon. Despite this within‐sediment coccolith dissolution flux, sediments below the calcite saturation horizon remain enriched in coccolith calcite. Combined with global seafloor hypsometry and calcium carbonate content, this enrichment suggests that globally, coccoliths may outweigh foraminifera in deep ocean sediments by a factor of 1.8.
Adaptive responses of marine diatoms to zinc scarcity and ecological implications

(Nature Research, 2022-04-14) Kellogg, Riss ; Moosburner, Mark A. ; Cohen, Natalie R. ; Hawco, Nicholas J. ; McIlvin, Matthew R. ; Moran, Dawn M. ; DiTullio, Giacomo R. ; Subhas, Adam V. ; Saito, Mak A.

Scarce dissolved surface ocean concentrations of the essential algal micronutrient zinc suggest that Zn may influence the growth of phytoplankton such as diatoms, which are major contributors to marine primary productivity. However, the specific mechanisms by which diatoms acclimate to Zn deficiency are poorly understood. Using global proteomic analysis, we identified two proteins (ZCRP-A/B, Zn/Co Responsive Protein A/B) among four diatom species that became abundant under Zn/Co limitation. Characterization using reverse genetic techniques and homology data suggests putative Zn/Co chaperone and membrane-bound transport complex component roles for ZCRP-A (a COG0523 domain protein) and ZCRP-B, respectively. Metaproteomic detection of ZCRPs along a Pacific Ocean transect revealed increased abundances at the surface (<200 m) where dZn and dCo were scarcest, implying Zn nutritional stress in marine algae is more prevalent than previously recognized. These results demonstrate multiple adaptive responses to Zn scarcity in marine diatoms that are deployed in low Zn regions of the Pacific Ocean.
In situ experimentally determined dissolution rates of biogenic calcites along a North Pacific transect between Hawaii and Alaska (KM1712 expedition) in August 2017

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-08-20) Berelson, William M. ; Adkins, Jess F. ; Subhas, Adam V. ; Dong, Sijia ; Naviaux, John D.

This dataset includes biogenic and inorganic calcite and aragonite dissolution rate data from the CDisK-IV cruise in the North Pacific Ocean, August 2017. We include niskin incubator alkalinity, pH, silicate, phosphate, and nitrate data, as well as calculated saturation state and dissolution rates. Rates are reported in units of g/g/day and also g/cm2/day, normalized by the specific surface areas of the materials used. Dissolution rates of inorganic aragonite and calcite, along with biogenic E. huxleyi liths, a planktic foraminifera assemblage, and a benthic foraminifera Amphistegina species, are provided, for 4 out of the 6 stations occupied on the cruise. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/856409
Global trends in the distribution of biogenic minerals in the ocean

(American Geophysical Union, 2023-02-03) Subhas, Adam V. ; Pavia, Frank J. ; Dong, Sijia ; Lam, Phoebe J.

The cycling of marine particulate matter is critical for sequestering carbon in the deep ocean and in marine sediments. Biogenic minerals such as calcium carbonate (CaCO3) and opal add density to more buoyant organic material, facilitating particle sinking and export. Here, we compile and analyze a global data set of particulate organic carbon (POC), particulate inorganic carbon (PIC, or CaCO3), and biogenic silica (bSi, or opal) concentrations collected using large volume pumps (LVPs). We analyze the distribution of all three biogenic phases in the small (1–53 μm) and large (>53 μm) size classes. Over the entire water column 76% of POC exists in the small size fraction. Similarly, the small size class contains 82% of PIC, indicating the importance of small‐sized coccolithophores to the PIC budget of the ocean. In contrast, 50% of bSi exists in the large size fraction, reflecting the larger size of diatoms and radiolarians compared with coccolithophores. We use PIC:POC and bSi:POC ratios in the upper ocean to document a consistent signal of shallow mineral dissolution, likely linked to biologically mediated processes. Sediment trap PIC:POC and bSi:POC are elevated with respect to LVP samples and increase strongly with depth, indicating the concentration of mineral phases and/or a deficit of POC in large sinking particles. We suggest that future sampling campaigns pair LVPs with sediment traps to capture the full particulate field, especially the large aggregates that contribute to mineral‐rich deep ocean fluxes, and may be missed by LVPs.
Pelagic calcium carbonate production and shallow dissolution in the North Pacific Ocean

(Nature Research, 2023-02-20) Ziveri, Patrizia ; Gray, William Robert ; Anglada-Ortiz, Griselda ; Manno, Clara ; Grelaud, Michael ; Incarbona, Alessandro ; Rae, James William Buchanan ; Subhas, Adam V. ; Pallacks, Sven ; White, Angelicque ; Adkins, Jess F. ; Berelson, William

Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO. Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate production in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolithophores dominate the living calcium carbonate (CaCO) standing stock, with coccolithophore calcite comprising ~90% of total CaCO production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO production is higher than the sinking flux of CaCO at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO production derived from satellite observations/biogeochemical modeling versus estimates from shallow sediment traps. We suggest future changes in the CaCO cycle and its impact on atmospheric CO will largely depend on how the poorly-understood processes that determine whether CaCO is remineralised in the photic zone or exported to depth respond to anthropogenic warming and acidification.
Suspended particles from in situ pumps on R/V Kilo Moana cruise KM1910 in June 2019

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-08-24) Black, Erin ; Maloney, Ashley ; Subhas, Adam V. ; Kenyon, Jennifer ; Church, Matthew J. ; White, Angelicque E. ; Goetze, Erica ; Ferron, Sara

Suspended particulate total carbon concentration, organic carbon concentration, inorganic carbon concentration, nitrogen concentration, and bulk isotope composition (C and N) from in situ McLane pumps in June 2019 at station ALOHA during cruise KM1910. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/853048
Ultrahigh-precision noble gas isotope analyses reveal pervasive subsurface fractionation in hydrothermal systems

(American Association for the Advancement of Science, 2023-03-16) Bekaert, David V. ; Barry, Peter H. ; Broadley, Michael W. ; Byrne, David J. ; Marty, Bernard ; Ramírez, Carlos J. ; de Moor, J Maarten ; Rodriguez, Alejandro ; Hudak, Michael R. ; Subhas, Adam V. ; Halldórsson, Saemundur A. ; Stefánsson, Andri ; Caracausi, Antonio ; Lloyd, Karen G. ; Giovannelli, Donato ; Seltzer, Alan M.

Mantle-derived noble gases in volcanic gases are powerful tracers of terrestrial volatile evolution, as they contain mixtures of both primordial (from Earth's accretion) and secondary (e.g., radiogenic) isotope signals that characterize the composition of deep Earth. However, volcanic gases emitted through subaerial hydrothermal systems also contain contributions from shallow reservoirs (groundwater, crust, atmosphere). Deconvolving deep and shallow source signals is critical for robust interpretations of mantle-derived signals. Here, we use a novel dynamic mass spectrometry technique to measure argon, krypton, and xenon isotopes in volcanic gas with ultrahigh precision. Data from Iceland, Germany, United States (Yellowstone, Salton Sea), Costa Rica, and Chile show that subsurface isotope fractionation within hydrothermal systems is a globally pervasive and previously unrecognized process causing substantial nonradiogenic Ar-Kr-Xe isotope variations. Quantitatively accounting for this process is vital for accurately interpreting mantle-derived volatile (e.g., noble gas and nitrogen) signals, with profound implications for our understanding of terrestrial volatile evolution.
Authigenic Formation of Clay Minerals in the Abyssal North Pacific

(American Geophysical Union, 2022-11-02) Steiner, Zvi ; Rae, James W. B. ; Berelson, William M. ; Adkins, Jess F. ; Hou, Yi ; Dong, Sijia ; Lampronti, Giulio I. ; Liu, Xuewu ; Achterberg, Eric P. ; Subhas, Adam V. ; Turchyn, Alexandra V.

Present estimates of the biogeochemical cycles of calcium, strontium, and potassium in the ocean reveal large imbalances between known input and output fluxes. Using pore fluid, incubation, and solid sediment data from North Pacific multi‐corer cores we show that, contrary to the common paradigm, the top centimeters of abyssal sediments can be an active site of authigenic precipitation of clay minerals. In this region, clay authigenesis is the dominant sink for potassium and strontium and consumes nearly all calcium released from benthic dissolution of calcium carbonates. These observations support the idea that clay authigenesis occurring over broad regions of the world ocean may be a major buffer for ocean chemistry on the time scale of the ocean overturning circulation, and key to the long‐term stability of Earth's climate.Key PointsNorth Pacific red clay sediments are a sink for marine calcium, strontium, and potassiumAuthigenic formation of clay minerals is prevalent in pelagic sediments throughout the North PacificThe main mechanism for clay formation is recrystallization of aluminosilicates, neoformation can occur in biogenic silica rich sediments
Barium in seawater: dissolved distribution, relationship to silicon, and barite saturation state determined using machine learning

(Copernicus Publications, 2023-09-13) Mete, Oyku Z. ; Subhas, Adam V. ; Kim, Heather H. ; Dunlea, Ann G. ; Whitmore, Laura M. ; Shiller, Alan M. ; Gilbert, Melissa ; Leavitt, William D. ; Horner, Tristan J.

Barium is widely used as a proxy for dissolved silicon and particulate organic carbon fluxes in seawater. However, these proxy applications are limited by insufficient knowledge of the dissolved distribution of Ba ([Ba]). For example, there is significant spatial variability in the barium–silicon relationship, and ocean chemistry may influence sedimentary Ba preservation. To help address these issues, we developed 4095 models for predicting [Ba] using Gaussian process regression machine learning. These models were trained to predict [Ba] from standard oceanographic observations using GEOTRACES data from the Arctic, Atlantic, Pacific, and Southern oceans. Trained models were then validated by comparing predictions against withheld [Ba] data from the Indian Ocean. We find that a model trained using depth, temperature, and salinity, as well as dissolved dioxygen, phosphate, nitrate, and silicate, can accurately predict [Ba] in the Indian Ocean with a mean absolute percentage deviation of 6.0 %. We use this model to simulate [Ba] on a global basis using these same seven predictors in the World Ocean Atlas. The resulting [Ba] distribution constrains the Ba budget of the ocean to 122(±7) × 1012 mol and reveals oceanographically consistent variability in the barium–silicon relationship. We then calculate the saturation state of seawater with respect to barite. This calculation reveals systematic spatial and vertical variations in marine barite saturation and shows that the ocean below 1000 m is at equilibrium with respect to barite. We describe a number of possible applications for our model outputs, ranging from use in mechanistic biogeochemical models to paleoproxy calibration. Our approach demonstrates the utility of machine learning in accurately simulating the distributions of tracers in the sea and provides a framework that could be extended to other trace elements. Our model, the data used in training and validation, and global outputs are available in Horner and Mete (2023, https://doi.org/10.26008/1912/bco-dmo.885506.2).

Subhas Adam V.

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